This invention relates generally to the structure and use of memory cards, flash drives and other small non-volatile memory devices.
Electronic circuit cards, including non-volatile memory cards, have been commercially implemented according to a number of well-known standards. Memory cards are used with personal computers, notebook computers, cellular telephones, personal digital assistants (PDAs), digital still cameras, digital movie cameras, portable audio players and other host electronic devices for the storage of large amounts of data. Such cards usually contain a re-programmable non-volatile semiconductor memory cell array along with a controller that controls operation of the memory cell array and interfaces with a host to which the card connected. Popular types of non-volatile memory cards include CompactFlash (CF), MultiMediaCard (MMC), Secure Digital (SD), miniSD, Memory Stick and TransFlash, each of which is sold by SanDisk Corporation, the assignee hereof.
Electrical contact patterns and types vary among the various memory cards. Several of the same type of card may be interchanged in a host card slot designed to accept that type of card but a receptacle designed for one type of card most often cannot accept any other type of card. Adaptors, both active and passive types, have been provided or proposed to allow some degree of interchangeability of electronic cards among such host devices. U.S. Pat. No. 6,266,724 of Harari et al. describes use of combinations of mother and daughter memory cards.
Other small, hand-held re-programmable non-volatile memory devices have also been made to interface with a computer or other type of host by including a Universal Serial Bus (USB) connector plug. These are especially convenient since personal computers, PDAs and other types of hosts commonly include one or more USB connector receptacles but may not have a receptacle slot that accepts any of above identified standard memory cards. Mechanical and electrical details of the USB connector and interface are provided by the “Universal Serial Bus Specification,” revision 2.0, dated Apr. 27, 2000. There are several USB flash drive products commercially available from SanDisk Corporation under its trademark Cruzer. USB flash drives are typically larger and shaped differently than the memory cards described above.
Another, higher transfer rate interface that has become commonplace on personal computers and other host devices is specified by the following standard of the Institute of Electrical and Electronics Engineers (IEEE): “IEEE Standard for a High Performance Serial Bus,” document no. IEEE 1394-1995, as amended by document nos. IEEE 1394a-2000 and IEEE 1394b-2002. A common commercial form of this bus interface is known as FireWire. Because of its higher speed, this interface is particularly useful for the transfer of large amounts of data to and from a host device.
A wireless communication capability has also been added to memory cards and flash drives in order to allow a notebook computer, PDA or other host device to use the card or flash drive for either wireless communication or non-volatile data storage, or both. These types of devices plug into the host in the same manner as the memory only device but provide the added capability of wireless communication of the host with other hosts, a Local Area Network (LAN), and the like. SanDisk Corporation manufactures combined memory and wireless communication devices as family of Wi-Fi Cards, for example.